C wrapper for ARM uqadd8

uqadd8x4.cpp

// See also __uqadd8

static inline uint8x4_t uqadd8x4 (uint8x4_t xs, uint8x4_t ys)
{
    uint8x4_t sums;
    asm volatile(
        "uqadd8 %[sums], %[xs], %[ys]" 
        : [sums] "=r" (sums) 
        : [xs] "%r" (xs), [ys] "r" (ys));
    return sums;
}